DVB-T (Digital Video Broadcasting-Terrestrial) is a transmission standard for terrestrial digital television broadcasting in Europe. The digitalization of television broadcasts has become widespread, not only in Europe, but in other countries as well. To yield more efficient use of frequencies, DVB-T2 standardization was started in 2006 for second generation terrestrial digital television broadcasting. Like the DVB-T, DVB-T2 adopts OFDM (Orthogonal Frequency Division Multiplexing).
FIG. 31 shows the transmission frame structure in DVB-T2. DVB-T2 utilizes a concept called the PLP (Physical Layer Pipe). One characteristic of DVB-T2 is that transmission parameters, such as the modulation method, coding ratio, and the like may be set independently for each PLP. The number of PLPs is at least 1 and at most 255. The example in FIG. 31 shows the case of 10 PLPs.
The following describes the transmission frame structure.Super Frame=N—T2 frames (N—T2=2−255)Frame=P1 symbol+P2 symbols+data symbolsP1 symbol=1 symbolP2 symbols=N—P2 symbols (N—P2 is unique based on FFT size)Data symbols=L_data symbols (L_data is variable, having an upper limit and a lower limit)
A P1 symbol is transmitted with an FFT size of 1 k and GI (GUARD INTERVAL)=½. The P1 symbol transmits seven bits of information, S1 and S2, with information on the FFT size and the like of subsequent P2 symbols and data symbols. The earlier portion of P2 symbols include L1 signaling data, and the remaining later portion includes main signal data. The data symbols include a continuation of the main signal data.
The L1 signaling data transmitted in P2 symbols is composed of L1-pre signaling data, which mainly transmits information shared by all of the PLPs, and L1-post signaling data, which mainly transmits information on each PLP. Note that details on the L1 signaling data, L1-pre signaling data, and L1-post signaling data transmitted in P2 symbols is listed in Non-Patent Literature 1.
FIG. 32 shows the structure of a transmitter 1000 conforming to DVB-T2 (see Non-Patent Literature 1: DVB-T2 transmission standards). The transmitter 1000 is provided with a main signal coder 1011, an L1 signaling data coder 1012, a frame builder 1013, and an OFDM signal generator 1014.
For each PLP of a main signal that is to be transmitted, the main signal coder 1011 performs error correction coding based on BCH coding and LDPC coding, performs interleaving, performs mapping onto I/Q coordinates, and outputs the mapping data for each PLP. Note that I represents the in-phase component, whereas Q represents the quadrature component.
The L1 signaling data coder 1012 performs error correction coding on the L1-pre signaling data and the L1-post signaling data, performs interleaving, performs mapping onto I/Q coordinates, and outputs the mapping data for the L1-pre signaling data and the L1-post signaling data.
The frame builder 1013 generates and outputs the transmission frame structure according to the DVB-T2 standard as shown in FIG. 31 using the mapping data for each PLP output by the main signal coder 1011 and the mapping data for the L1-pre signaling data and the L1-post signaling data output by the L1 signaling data coder 1012.
To the transmission frame structure according to the DVB-T2 standard as output by the frame builder 1013, the OFDM signal generator 1014 adds a pilot signal, performs an IFFT (Inverse Fast Fourier Transform), inserts a GI, and inserts a P1 symbol, outputting a transmission signal according to DVB-T2.
The following provides details on the L1 signaling data coder 1012. As shown in FIG. 32, the L1 signaling data coder 1012 is provided with an L1 signaling data generator 1021, an L1 error correction coder 1022, an L1-pre mapper 1023, an L1-post bit interleaver 1025, and an L1-post mapper 1026. The L1 error correction coder 1022 is provided with an L1-pre error correction coder 1031 and an L1-post error correction coder 1032.
In the L1 signaling data coder 1012, the L1 signaling data generator 1021 generates L1 signaling data from transmission parameters, i.e. transforms transmission parameters into L1 signaling data (L1-pre signaling data and L1-post signaling data) and outputs the L1 signaling data. The L1-pre error correction coder 1031 performs error correction coding, based on BCH coding and LDPC coding, on the L1-pre signaling data. The L1-pre mapper 1023 maps the error correction coded L1-pre signaling data to I/Q coordinates, outputting mapping data for the L1-pre signaling data.
On the other hand, the L1-post error correction coder 1032 performs error correction coding, based on BCH coding and LDPC coding, on the L1-post signaling data. The L1-post bit interleaver 1025 interleaves the error correction coded L1-post signaling data in units of bits. The L1-post mapper 1026 maps the L1-post signaling data, which has been error correction coded and interleaved in units of bits, to I/Q coordinates, outputting mapping data for the L1-post signaling data.
FIG. 33 shows the structure of a receiver 1100 conforming to DVB-T2 (see Non-Patent Literature 2: DVB-T2 implementation guidelines). The receiver 1100 is provided with an antenna 1111, a tuner 1112, an A/D converter 1113, an OFDM demodulator 1114, a selected PLP/L1 signaling data extraction unit 1115, a main signal decoder 1116, and an L1 signaling data decoder 1117.
The antenna 1111 receives radio waves. The tuner 1112 selectively receives an OFDM signal of a desired channel and down-converts the signal to a predetermined band. The A/D converter 1113 converts the signal output by the tuner 1112 from analog to digital. The OFDM demodulator 1114 performs OFDM demodulation on the signal output by the A/D converter 1113 and outputs mapping data in I/Q coordinates.
The selected PLP/L1 signaling data extraction unit 1115 extracts the L1-pre signaling data and the L1-post signaling data from the OFDM demodulated signal (mapping data in I/Q coordinates), outputting the extracted information. Following a selected PLP instruction, the selected PLP/L1 signaling data extraction unit 1115 also extracts the PLP (main signal) selected by the user. Note that the selected PLP/L1 signaling data extraction unit 1115 extracts the PLP (main signal) selected by the user after processing by the L1 signaling data decoder 1117, using the transmission parameters output by the L1 signaling data decoder 1117.
The L1 signaling data decoder 1117 demaps the extracted L1-pre signaling data and L1-post signaling data from I/Q coordinates and deinterleaves these data that were interleaved at the transmitting end. The L1 signaling data decoder 1117 then performs error correction decoding based on LDPC decoding and BCH decoding, analyzes the decoded (reproduced) L1 signaling data, and outputs transmission parameters.
Based on the transmission parameters output by the L1 signaling data decoder 1117, the main signal decoder 1116 demaps the extracted PLP (main signal) from I/Q coordinates and deinterleaves the PLP that was interleaved at the transmitting end. The main signal decoder 1116 then performs error correction decoding based on LDPC decoding and BCH decoding and outputs the decoded (reproduced) main signal.
The following provides details on the L1 signaling data decoder 1117. As shown in FIG. 33, the L1 signaling data decoder 1117 is provided with an L1-pre demapper 1121, an L1-post demapper 1122, an L1-post bit deinterleaver 1123, an L1 error correction decoder 1124, and an L1 signaling data analyzer 1125. The L1 error correction decoder 1124 is provided with an L1-pre error correction decoder 1131 and an L1-post error correction decoder 1132.
In the L1 signaling data decoder 1117, the L1-pre demapper 1121 demaps the extracted L1-pre signaling data from I/Q coordinates. The L1-pre error correction decoder 1131 performs error correction decoding of the demapped L1-pre signaling data based on LDPC decoding and BCH decoding.
On the other hand, the L1-post demapper 1122 demaps the extracted L1-post signaling data from I/Q coordinates. The L1-post bit deinterleaver 1123 deinterleaves the demapped L1-post signaling data that was interleaved at the transmitting end in units of bits. The L1-post error correction decoder 1132 performs error correction decoding of the bit-deinterleaved L1-post signaling data based on LDPC decoding and BCH decoding.
The L1 signaling data analyzer 1125 analyzes the decoded (reproduced) L1-pre signaling data and the L1-post signaling data and outputs the transmission parameters. Note that among the L1-post signaling data, the L1 signaling data analyzer 1125 follows a selected PLP instruction to extract and analyze the transmission parameters for the PLP selected by the user.